1. Field of the Invention
The present invention relates to a camera having a picture taking optical system including a main lens system and a sub lens system, for example, said camera being operable in a wide-angle mode only by the use of the main lens system and in a telephoto mode by the use of the combination of the main lens system with the sub lens system, said camera having a dust cover adapted to protect the optical system.
2. Description of the Prior Art
One of the prior art cameras of such a type is disclosed in Japanese Laid-open Patent Application No. 145930/1983. This camera comprises a drive mechanism for moving a sub lens between a position in which it is inserted into the optical path of a main lens and a position in which the sub lens is retracted from said optical path. In the inserted position, the sub lens is combined with the main lens to form a picture taking optical system. In the retracted position of the sub lens, another picture taking optical system is defined only by the main lens.
On designing of the above drive mechanism, it is most important that the combined optical system is formed under such a state that the main lens is exactly aligned with the sub lens with respect to the optical axis. Moreover, the movable sub lens must firmly be held stationary relative to the camera housing so as to be unaffected by external impact or vibration. Also, it is desirable that the camera be provided with a dust cover to protect the optical system.